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RFC 7678

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Attribute-Value Pairs for Provisioning Customer Equipment Supporting IPv4-Over-IPv6 Transitional Solutions

 


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Internet Engineering Task Force (IETF)                           C. Zhou
Request for Comments: 7678                           Huawei Technologies
Category: Standards Track                                      T. Taylor
ISSN: 2070-1721                                     PT Taylor Consulting
                                                                  Q. Sun
                                                           China Telecom
                                                            M. Boucadair
                                                          France Telecom
                                                            October 2015


  Attribute-Value Pairs for Provisioning Customer Equipment Supporting
                 IPv4-Over-IPv6 Transitional Solutions

Abstract

   During the transition from IPv4 to IPv6, customer equipment may have
   to support one of the various transition methods that have been
   defined for carrying IPv4 packets over IPv6.  This document
   enumerates the information that needs to be provisioned on a customer
   edge router to support a list of transition techniques based on
   tunneling IPv4 in IPv6, with a view to defining reusable components
   for a reasonable transition path between these techniques.  To the
   extent that the provisioning is done dynamically, Authentication,
   Authorization, and Accounting (AAA) support is needed to provide the
   information to the network server responsible for passing the
   information to the customer equipment.  This document specifies
   Diameter (RFC 6733) Attribute-Value Pairs (AVPs) to be used for that
   purpose.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc7678.

Page 2 
Copyright Notice

   Copyright (c) 2015 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   4
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   5
   2.  Description of the Parameters Required by Each Transition
       Method  . . . . . . . . . . . . . . . . . . . . . . . . . . .   5
     2.1.  Parameters for Dual-Stack Lite (DS-Lite)  . . . . . . . .   6
     2.2.  Lightweight 4over6 (lw4o6)  . . . . . . . . . . . . . . .   6
     2.3.  Port Set Specification  . . . . . . . . . . . . . . . . .   7
     2.4.  Mapping of Address and Port with Encapsulation (MAP-E)  .   7
     2.5.  Parameters for Multicast  . . . . . . . . . . . . . . . .   8
     2.6.  Summary and Discussion  . . . . . . . . . . . . . . . . .   9
   3.  Attribute-Value Pair Definitions  . . . . . . . . . . . . . .   9
     3.1.  IP-Prefix-Length AVP  . . . . . . . . . . . . . . . . . .  10
     3.2.  Border-Router-Name AVP  . . . . . . . . . . . . . . . . .  10
     3.3.  64-Multicast-Attributes AVP . . . . . . . . . . . . . . .  10
       3.3.1.  ASM-mPrefix64 AVP . . . . . . . . . . . . . . . . . .  11
       3.3.2.  SSM-mPrefix64 AVP . . . . . . . . . . . . . . . . . .  11
       3.3.3.  Delegated-IPv6-Prefix AVP as uPrefix64  . . . . . . .  12
     3.4.  Tunnel-Source-Pref-Or-Addr AVP  . . . . . . . . . . . . .  12
       3.4.1.  Delegated-IPv6-Prefix as the IPv6 Binding Prefix  . .  12
       3.4.2.  Tunnel-Source-IPv6-Address AVP  . . . . . . . . . . .  12
     3.5.  Port-Set-Identifier . . . . . . . . . . . . . . . . . . .  13
     3.6.  Lw4o6-Binding AVP . . . . . . . . . . . . . . . . . . . .  13
       3.6.1.  Lw4o6-External-IPv4-Addr AVP  . . . . . . . . . . . .  14
     3.7.  MAP-E-Attributes  . . . . . . . . . . . . . . . . . . . .  14
     3.8.  MAP-Mesh-Mode . . . . . . . . . . . . . . . . . . . . . .  15
     3.9.  MAP-Mapping-Rule  . . . . . . . . . . . . . . . . . . . .  15
       3.9.1.  Rule-IPv4-Addr-Or-Prefix AVP  . . . . . . . . . . . .  16
       3.9.2.  Rule-IPv6-Prefix AVP  . . . . . . . . . . . . . . . .  16
       3.9.3.  EA-Field-Length AVP . . . . . . . . . . . . . . . . .  17
   4.  Attribute-Value Pair Flag Rules . . . . . . . . . . . . . . .  18
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  19
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  19
     6.1.  Man-In-The-Middle (MITM) Attacks  . . . . . . . . . . . .  19
     6.2.  Privacy . . . . . . . . . . . . . . . . . . . . . . . . .  20
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  20
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .  20
     7.2.  Informative References  . . . . . . . . . . . . . . . . .  21
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .  22
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  23

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1.  Introduction

   A number of transition techniques have been defined to allow IPv4
   packets to pass between hosts and IPv4 networks over an intervening
   IPv6 network while minimizing the number of public IPv4 addresses
   that need to be consumed by the hosts.  Different operators will
   deploy different technologies, and sometimes one operator will use
   more than one technology depending on what is supported by the
   available equipment and upon other factors both technical and
   economic.

   Each technique requires the provisioning of some subscriber-specific
   information on the customer edge device.  The provisioning may be by
   DHCPv6 [RFC3315] or by some other method.  This document is
   indifferent to the specific provisioning technique used but assumes a
   deployment in which that information is managed by AAA
   (Authentication, Authorization, and Accounting) servers.  It further
   assumes that this information is delivered to intermediate network
   nodes for onward provisioning using the Diameter protocol [RFC6733].

   As described below, in the particular case where the Lightweight
   4over6 (lw4o6) [RFC7596] transition method has been deployed, per-
   subscriber-site information almost identical to that passed to the
   subscriber site [RFC7598] also needs to be delivered to the border
   router serving that site.  The Diameter protocol may be used for this
   purpose too.

   This document analyzes the information required to configure the
   customer edge equipment for the following set of transition methods:

   o  Dual-Stack Lite (DS-Lite) [RFC6333],

   o  Lightweight 4over6 (lw4o6) [RFC7596], and

   o  Mapping of Address and Port with Encapsulation (MAP-E) [RFC7597].

   [DSLITE-MULTICAST] specifies a generic solution for delivery of IPv4
   multicast services to IPv4 clients over an IPv6 multicast network.
   The solution was developed with DS-Lite in mind but it is not limited
   to DS-Lite.  As such, it applies also for lw4o6 and MAP-E.  This
   document analyzes the information required to configure the customer
   edge equipment for the support of multicast in the context of DS-
   Lite, MAP-E, and lw4o6 in particular.

   On the basis of those analyses, it specifies a number of Attribute-
   Value Pairs (AVPs) to allow the necessary subscriber-site-specific
   configuration information to be carried in Diameter.

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   This document doesn't specify any new commands or Application IDs.
   The specified AVPs could be used for any Diameter application
   suitable for provisioning.

1.1.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

   The abbreviation CPE stands for Customer Premise Equipment.  It
   denotes the equipment at the customer edge that terminates the
   customer end of an IPv6 transitional tunnel.  This will usually be a
   router but could be a host directly connected to the network.  In
   some documents (e.g., [RFC7597]), this functional entity is called CE
   (Customer Edge).

   The term "tunnel source address" is used to denote the IPv6 source
   address used in the outer header of packets sent from the CPE through
   an lw4o6 transitional tunnel to the border router.

2.  Description of the Parameters Required by Each Transition Method

   This section reviews the parameters that need to be provisioned for
   each of the transition methods listed above.  This enumeration
   provides the justification for the AVPs defined in the next section.

   A means is required to indicate which transition method(s) a given
   subscriber wants to use.  The approach taken in this document is to
   specify Grouped AVPs specific to lw4o6 and MAP-E.  The operator can
   control which of these two transition methods a given subscriber uses
   by ensuring that AAA passes only the Grouped AVP relevant to that
   method.  A Grouped AVP is unnecessary for DS-Lite since AAA has only
   to provide the Fully Qualified Domain Name (FQDN) of the DS-Lite
   Address Family Transition Router (AFTR) (see Section 2.1).  Hence,
   when no Grouped AVP is provided either for lw4o6 or MAP-E and only
   the AFTR's FQDN is present, this indicates that the subscriber
   equipment will use the DS-Lite transition method.  Provisioning of
   multicast is an orthogonal activity since it is independent of the
   transition method.

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2.1.  Parameters for Dual-Stack Lite (DS-Lite)

   DS-Lite is documented in [RFC6333].  The Basic Bridging BroadBand
   (B4) element at the customer premises needs to discover the IPv6
   address of the AFTR (border router).  For the reasons discussed in
   Section 3.2, the AAA server provisions the B4 element with the AFTR's
   FQDN that is passed to a B4's IP resolution library.  The AFTR's FQDN
   is contained in the Border-Router-Name AVP (see Section 3.2).

   The B4 element could also be configured with the IPv4 address of the
   B4 interface facing the tunnel, with valid values from 192.0.0.2 to
   192.0.0.7 and the default value of 192.0.0.2 in the absence of
   provisioning.  Provisioning such information through AAA is
   problematic because it is most likely used in a case where multiple
   B4 instances occupy the same device.  This document therefore assumes
   that the B4 interface address is determined by other means than AAA
   (implementation dependent or static assignment).

2.2.  Lightweight 4over6 (lw4o6)

   Lightweight 4over6 (lw4o6) is documented in [RFC7596].  Lw4o6
   requires four items to be provisioned to the customer equipment:

   o  an IPv6 address of the border router.

   o  an IPv6 prefix used by the CPE to construct the tunnel source
      address.  In the terminology of [RFC7596], this is the IPv6
      Binding Prefix.

   o  an IPv4 address to be used on the external side of the CPE.

   o  if the IPv4 address is shared, a specification of the port set the
      subscriber site is allowed to use.  Please see the description in
      Section 2.3.  For lw4o6, all three of the parameters 'a', 'k', and
      the Port Set Identifier (PSID) described in that section are
      required.  The default value of the offset parameter 'a' is 0.

   As discussed in Section 4 of [RFC7596], it is necessary to
   synchronize this configuration with corresponding per-subscriber
   configuration at the border router.  The border router information
   consists of the same public IPv4 address and port set parameters that
   are passed to the CPE, bound together with the full /128 IPv6 address
   (not just the Binding Prefix) configured as the tunnel source address
   at the CPE.

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2.3.  Port Set Specification

   When an external IPv4 address is shared, lw4o6 and MAP-E restrict the
   CPE to use of a subset of all available ports on the external side.
   Both transition methods use the algorithm defined in Appendix B of
   [RFC7597] to derive the values of the port numbers in the port set.
   This algorithm features three parameters, describing the positioning
   and value of the PSID within each port number of the generated set:

   o  an offset 'a' from the beginning of the port number to the first
      bit of the PSID;

   o  the length 'k' of the PSID within the port number, in bits; and

   o  the value of the PSID itself.

2.4.  Mapping of Address and Port with Encapsulation (MAP-E)

   Mapping of Address and Port with Encapsulation (MAP-E) is described
   in [RFC7597].  MAP-E requires the provisioning of the following per-
   subscriber information at the customer edge device:

   o  the IPv6 address of one or more border routers, or in MAP-E
      terminology, MAP-E border relays.

   o  the unique end-user IPv6 prefix for the customer edge device.
      This may be provided by AAA or acquired by other means.

   o  the Basic Mapping Rule for the customer edge device.  This
      includes the following parameters:

      *  the Rule IPv6 prefix and length.

      *  the Rule IPv4 prefix and length.  A prefix length of 0
         indicates that the entire IPv4 address or prefix is coded in
         the Extended Address (EA) bits of the end-user IPv6 prefix
         rather than in the mapping rule.

      *  the number of EA bits included in the end-user IPv6 prefix.

      *  port set parameters giving the set of ports the CPE is allowed
         to use when the IPv4 address is shared.  Please see the
         description of these parameters in Section 2.3.  At a minimum,
         the offset parameter 'a' is required.  For MAP-E, this has the
         default value 6.  The parameters 'k' and PSID are needed if
         they cannot be derived from the mapping rule information and
         the EA bits (final case of Section 5.2 of [RFC7597]).

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   o  whether the device is to operate in Mesh or Hub-and-Spoke mode.

   o  in mesh mode only, zero or more Forwarding Mapping Rules described
      by the same set of parameters as the Basic Mapping Rule.

   As indicated in the first bullet in Section 5 of [RFC7597], a MAP CPE
   can be provisioned with multiple end-user IPv6 prefixes, each
   associated with its own Basic Mapping Rule.  This does not change the
   basic requirement for representation of the corresponding information
   in the form of Diameter AVPs, but adds a potential requirement for
   multiple instances of this information to be present in the Diameter
   message, differing in the value of the end-user IPv6 prefix (in
   contrast to the Forward Mapping Rule instances).

   The border router needs to be configured with the superset of the
   Mapping Rules passed to the customer sites it serves.  Since this
   requirement does not require direct coordination with CPE
   configuration in the way lw4o6 does, it is out of scope of the
   present document.  However, the AVPs defined here may be useful if a
   separate Diameter application is used to configure the border router.

2.5.  Parameters for Multicast

   [DSLITE-MULTICAST] specifies a generic solution for delivery of IPv4
   multicast services to IPv4 clients over an IPv6 multicast network.
   In particular, the solution can be deployed in a DS-Lite context but
   is also adaptable to lw4o6 and MAP-E.  For example, [PREFIX-OPTION]
   specifies how DHCPv6 [RFC3315] can be used to provision multicast-
   related information.  The following lists the multicast-related
   information that needs to be provisioned:

   o  ASM-mPrefix64: the IPv6 multicast prefix to be used to synthesize
      the IPv4-embedded IPv6 addresses of the multicast groups in the
      Any-Source Multicast (ASM) mode.  This is achieved by
      concatenating the ASM-mPrefix64 and an IPv4 multicast address; the
      IPv4 multicast address is inserted in the last 32 bits of the
      IPv4-embedded IPv6 multicast address.

   o  SSM-mPrefix64: the IPv6 multicast prefix to be used to synthesize
      the IPv4-embedded IPv6 addresses of the multicast groups in the
      Source-Specific Multicast (SSM) [RFC4607] mode.  This is achieved
      by concatenating the SSM-mPrefix64 and an IPv4 multicast address;
      the IPv4 multicast address is inserted in the last 32 bits of the
      IPv4-embedded IPv6 multicast address.

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   o  uPrefix64: the IPv6 unicast prefix to be used in SSM mode for
      constructing the IPv4-embedded IPv6 addresses representing the
      IPv4 multicast sources in the IPv6 domain. uPrefix64 may also be
      used to extract the IPv4 address from the received multicast data
      flows.  The address mapping follows the guidelines documented in
      [RFC6052].

2.6.  Summary and Discussion

   There are two items that are common to the different transition
   methods, and the corresponding AVPs to carry them can be reused:

   o  a representation of the IPv6 address of a border router.

   o  a set of prefixes for delivery of multicast services to IPv4
      clients over an IPv6 multicast network.

   [RFC6519] sets a precedent for representation of the IPv6 address of
   a border router as an FQDN.  This can be dereferenced to one or more
   IP addresses by the provisioning system before being passed to the
   customer equipment or left as an FQDN as it is in [RFC6334].

   The remaining requirements are transition-method specific:

   o  for lw4o6, a representation of a binding between (1) either the
      IPv6 Binding Prefix or a full /128 IPv6 address, (2) a public IPv4
      address, and (3) (if the IPv4 address is shared) a port set
      identifier.

   o  for MAP-E, a representation of the unique end-user IPv6 prefix for
      the CPE, if not provided by other means.

   o  for MAP-E, a representation of a Mapping Rule.

   o  for MAP-E, an indication of whether Mesh mode or Hub-and-Spoke
      mode is to be used.

3.  Attribute-Value Pair Definitions

   This section provides the specifications for the AVPs needed to meet
   the requirements summarized in Section 2.6.

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3.1.  IP-Prefix-Length AVP

   The IP-Prefix-Length AVP (AVP code 632) is of type Unsigned32.  It
   provides the length of an IPv4 or IPv6 prefix.  Valid values are from
   0 to 32 for IPv4 and from 0 to 128 for IPv6.  Tighter limits are
   given below for particular contexts of use of this AVP.

   Note that the IP-Prefix-Length AVP is only relevant when associated
   with an IP-Address AVP in a Grouped AVP.

3.2.  Border-Router-Name AVP

   Following on the precedent set by [RFC6334] and [RFC6519], this
   document identifies a border router using an FQDN rather than an
   address.  The Border-Router-Name AVP (AVP Code 633) is of type
   OctetString.  The FQDN encoding MUST follow the Name Syntax defined
   in [RFC1035], [RFC1123], and [RFC2181] and are represented in ASCII
   form.  Note, if Internationalized Domain Names (IDNs) are used,
   A-labels defined in [RFC5891] must be used (see Appendix D of
   [RFC6733]).

3.3.  64-Multicast-Attributes AVP

   The 64-Multicast-Attributes AVP (AVP Code 634) is of type Grouped.
   It contains the multicast-related IPv6 prefixes needed for providing
   IPv4 multicast over IPv6 using DS-Lite, MAP-E, or lw4o6, as mentioned
   in Section 2.5.

   The syntax is shown in Figure 1.

           64-Multicast-Attributes  ::= < AVP Header: 634 >
                                        [ ASM-mPrefix64 ]
                                        [ SSM-mPrefix64 ]
                                        [ Delegated-IPv6-Prefix ]
                                       *[ AVP ]

                   Figure 1: 64-Multicast-Attributes AVP

   The 64-Multicast-Attributes AVP MUST include the ASM-mPrefix64 AVP or
   the SSM-mPrefix64 AVP, and it MAY include both.

   The Delegated-IPv6-Prefix AVP MUST be present when the SSM-mPrefix64
   AVP is present.  The Delegated-IPv6-Prefix AVP MAY be present when
   the ASM-mPrefix64 AVP is present.

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3.3.1.  ASM-mPrefix64 AVP

   The ASM-mPrefix64 AVP (AVP Code 635) conveys the value of ASM-
   mPrefix64 as mentioned in Section 2.5.  The ASM-mPrefix64 AVP is of
   type Grouped, as shown in Figure 2.

             ASM-mPrefix64  ::= < AVP Header: 635 >
                                { IP-Address }
                                { IP-Prefix-Length }
                               *[ AVP ]

                        Figure 2: ASM-mPrefix64 AVP

   IP-Address (AVP code 518) is defined in [RFC5777] and is of type
   Address.  Within the ASM-mPrefix64 AVP, it provides the value of an
   IPv6 prefix.  The AddressType field in IP-Address MUST have value 2
   (IPv6).  The conveyed multicast IPv6 prefix MUST belong to the ASM
   range.  Unused bits in IP-Address beyond the actual prefix MUST be
   set to zeroes by the sender and ignored by the receiver.

   The IP-Prefix-Length AVP (AVP code 632) provides the actual length of
   the prefix contained in the IP-Address AVP.  Within the ASM-mPrefix64
   AVP, valid values of the IP-Prefix-Length AVP are from 24 to 96.

3.3.2.  SSM-mPrefix64 AVP

   The SSM-mPrefix64 AVP (AVP Code 636) conveys the value of SSM-
   mPrefix64 as mentioned in Section 2.5.  The SSM-mPrefix64 AVP is of
   type Grouped, as shown in Figure 3.

             SSM-mPrefix64  ::= < AVP Header: 636 >
                                { IP-Address }
                                { IP-Prefix-Length }
                               *[ AVP ]

                        Figure 3: SSM-mPrefix64 AVP

   IP-Address (AVP code 518) provides the value of an IPv6 prefix.  The
   AddressType field in IP-Address MUST have value 2 (IPv6).  The
   conveyed multicast IPv6 prefix MUST belong to the SSM range.  Unused
   bits in IP-Address beyond the actual prefix MUST be set to zeroes by
   the sender and ignored by the receiver.

   The IP-Prefix-Length AVP (AVP code 632) provides the actual length of
   the prefix contained in the IP-Address AVP.

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3.3.3.  Delegated-IPv6-Prefix AVP as uPrefix64

   Within the 64-Multicast-Attributes AVP, the Delegated-IPv6-Prefix AVP
   (AVP Code 123) conveys the value of uPrefix64, a unicast IPv6 prefix,
   as mentioned in Section 2.5.  The Delegated-IPv6-Prefix AVP is
   defined in [RFC4818].  As specified by [RFC6052], the value in the
   Prefix-Length field MUST be one of 32, 48, 56, 64, or 96.

3.4.  Tunnel-Source-Pref-Or-Addr AVP

   The Tunnel-Source-Pref-Or-Addr AVP (AVP Code 637) conveys either the
   IPv6 Binding Prefix or the tunnel source address on the CPE, as
   described in Section 2.2.  The Tunnel-Source-Pref-Or-Addr AVP is of
   type Grouped with syntax as shown in Figure 4.  The Tunnel-Source-
   Pref-Or-Addr AVP MUST contain either the Delegated-IPv6-Prefix AVP or
   the Tunnel-Source-IPv6-Address AVP, not both.

          Tunnel-Source-Pref-Or-Addr  ::= < AVP Header: 637 >
                                          [ Delegated-IPv6-Prefix ]
                                          [ Tunnel-Source-IPv6-Address ]
                                         *[ AVP ]

                 Figure 4: Tunnel-Source-Pref-Or-Addr AVP

   This AVP is defined separately from the lw4o6-Binding AVP (which
   includes it) to provide flexibility in the transport of the tunnel
   source address from the provisioning system to AAA while also
   supporting the provision of a complete binding to the lw4o6 border
   router.

3.4.1.  Delegated-IPv6-Prefix as the IPv6 Binding Prefix

   The Delegated-IPv6-Prefix AVP (AVP code 123) is of type OctetString
   and is defined in [RFC4818].  Within the Tunnel-Source-Pref-Or-Addr
   AVP, it conveys the IPv6 Binding Prefix assigned to the CPE.  Valid
   values in the Prefix-Length field are from 0 to 128 (full address).

3.4.2.  Tunnel-Source-IPv6-Address AVP

   The Tunnel-Source-IPv6-Address AVP (AVP code 638) is of type Address.
   It provides the address assigned by the CPE to identify its local end
   of an lw4o6 tunnel.  The AddressType field in this AVP MUST be set to
   2 (IPv6).

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3.5.  Port-Set-Identifier

   The Port-Set-Identifier AVP (AVP Code 639) is a structured
   OctetString with four octets of data, hence a total AVP length of 12.
   The description of the structure that follows refers to the
   parameters described in Section 2.3 (see Figure 5).

   o  The first (high-order) octet is the Offset field.  It is
      interpreted as an 8-bit unsigned integer giving the offset 'a'
      from the beginning of a port number to the beginning of the PSID
      to which that port belongs.  Valid values are from 0 to 15.

   o  The next octet, the PSIDLength, is also interpreted as an 8-bit
      unsigned integer and gives the length 'k' in bits of the PSID.
      Valid values are from 0 to (16 - a).  A value of 0 indicates that
      the PSID is not present (probable case for MAP-E, see
      Section 2.4), and the PSIDValue field MUST be ignored.

   o  The final two octets contain the PSIDValue field.  They give the
      value of the PSID itself, right justified within the field.  That
      is, the value of the PSID occupies the 'k' lowest-order bits of
      the PSIDValue field.

       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |    Offset     |    Length     |        PSID  Value            |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                            Figure 5: Port Set

3.6.  Lw4o6-Binding AVP

   The Lw4o6-Binding AVP (AVP Code 640) is of type Grouped.  It contains
   the elements of configuration that constitute the binding between an
   lw4o6 tunnel and IPv4 packets sent through that tunnel, as described
   in Section 2.2.

                    Lw4o6-Binding  ::= < AVP Header: 640 >
                                       { Tunnel-Source-Pref-Or-Addr }
                                       { Lw4o6-External-IPv4-Addr }
                                       [ Port-Set-Identifier ]
                                      *[ AVP ]

                        Figure 6: Lw4o6-Binding AVP

Top      ToC       Page 14 
   The Tunnel-Source-Pref-Or-Addr AVP is defined in Section 3.4 and
   provides either the Binding Prefix or the full IPv6 tunnel source
   address.

   The Lw4o6-External-IPv4-Addr AVP is defined in Section 3.6.1.

   The Port-Set-Identifier AVP is defined in Section 3.5.  It identifies
   the specific set of ports assigned to the lw4o6 tunnel when the IPv4
   address is being shared.

3.6.1.  Lw4o6-External-IPv4-Addr AVP

   The Lw4o6-External-IPv4-Addr AVP (AVP Code 641) uses the Address
   derived data format defined in Section 4.3.1 of [RFC6733].  It
   provides the CPE's external IPv4 address within the lw4o6 tunnel
   associated with the given binding.  The AddressType field MUST be set
   to 1 (IPv4), and the total length of the AVP MUST be 14 octets.

3.7.  MAP-E-Attributes

   The MAP-E-Attributes AVP (AVP Code 642) is of type Grouped.  It
   contains the configuration data identified in Section 2.4 for all of
   the mapping rules (Basic and Forwarding) in a single MAP domain.
   Multiple instances of this AVP will be present if the CPE belongs to
   multiple MAP domains.

                    MAP-E-Attributes  ::= < AVP Header: 642 >
                                        1*{ Border-Router-Name }
                                        1*{ MAP-Mapping-Rule }
                                          [ MAP-Mesh-Mode ]
                                          [ Delegated-IPv6-Prefix ]
                                         *[ AVP ]

                      Figure 7: MAP-E-Attributes AVP

   The Border-Router-Name AVP is defined in Section 3.2.  It provides
   the FQDN of a MAP border relay at the edge of the MAP domain to which
   the containing MAP-E-Attributes AVP relates.  At least one instance
   of this AVP MUST be present.

   The MAP-Mapping-Rule AVP is defined in Section 3.9.  At least one
   instance of this AVP MUST be present.  If the MAP-E domain supports
   Mesh mode (indicated by the presence of the MAP-Mesh-Mode AVP),
   additional MAP-Mapping-Rule instances MAY be present.  If the MAP-E
   domain is operating in Hub-and-Spoke mode; additional MAP-Mapping-
   Rule instances MUST NOT be present.

Top      ToC       Page 15 
   The MAP-Mesh-Mode AVP is defined in Section 3.8.  The absence of the
   Mesh mode indicator attribute indicates that the CPE is required to
   operate in Hub-and-Spoke mode.

   The Delegated-IPv6-Prefix AVP (AVP Code 123) provides the end-user
   IPv6 prefix assigned to the CPE for the MAP domain to which the
   containing MAP-E-Attributes AVP relates.  The AVP is defined in
   [RFC4818].  Valid values of the Prefix-Length field range from 0 to
   128.

   The Delegated-IPv6-Prefix AVP is optional because, depending on
   deployment, the end-user IPv6 prefix may be provided by AAA or by
   other means.  If multiple instances of the MAP-E-Attributes AVP
   containing the Delegated-IPv6-Prefix AVP are present, each instance
   of the latter MUST have a different value.

3.8.  MAP-Mesh-Mode

   The MAP-Mesh-Mode AVP (AVP Code 643) is of type Enumerated and
   indicates whether the CPE has to operate in Mesh or Hub-and-Spoke
   mode when using MAP-E.  The following values are supported:

      0 MESH

      1 HUB_AND_SPOKE

   The absence of the Mesh mode indicator attribute indicates that the
   CPE is required to operate in Hub-and-Spoke mode.

3.9.  MAP-Mapping-Rule

   The MAP-Mapping-Rule AVP (AVP Code 644) is of type Grouped and is
   used only in conjunction with MAP-based transition methods.  Mapping
   rules are required both by the MAP border relay and by the CPE.  The
   components of the MAP-Mapping-Rule AVP provide the contents of a
   mapping rule as described in Section 2.4.

   The syntax of the MAP-Mapping-Rule AVP is as follows:

            MAP-Mapping-Rule  ::= < AVP Header: 644 >
                                  { Rule-IPv4-Addr-Or-Prefix }
                                  { Rule-IPv6-Prefix    }
                                  { EA-Field-Length     }
                                  { Port-Set-Identifier }
                                 *[ AVP ]

                      Figure 8: MAP-Mapping-Rule AVP

Top      ToC       Page 16 
   The Rule-IPv4-Addr-Or-Prefix, Rule-IPv6-Prefix, EA-Field-Length, and
   Port-Set-Identifier AVPs MUST all be present.

   The Port-Set-Identifier AVP provides information to identify the
   specific set of ports assigned to the CPE.  For more information, see
   Sections 2.4 and 2.3.  The Port-Set-Identifier AVP is defined in
   Section 3.5.

3.9.1.  Rule-IPv4-Addr-Or-Prefix AVP

   The Rule-IPv4-Addr-Or-Prefix AVP (AVP Code 645) conveys the Rule IPv4
   prefix and length as described in Section 2.4.  The Rule-IPv4-Addr-
   Or-Prefix AVP is of type Grouped, as shown in Figure 9.

             Rule-IPv4-Addr-Or-Prefix  ::= < AVP Header: 645 >
                                           { IP-Address }
                                           { IP-Prefix-Length }
                                          *[ AVP ]

                  Figure 9: Rule-IPv4-Addr-Or-Prefix AVP

   IP-Address (AVP code 518) is defined in [RFC5777] and is of type
   Address.  Within the Rule-IPv4-Addr-Or-Prefix AVP, it provides the
   value of a unicast IPv4 address or prefix.  The AddressType field in
   IP-Address MUST have value 1 (IPv4).  Unused bits in IP-Address
   beyond the actual prefix MUST be set to zeroes by the sender and
   ignored by the receiver.

   The IP-Prefix-Length AVP (AVP code 632) provides the actual length of
   the prefix contained in the IP-Address AVP.  Within the Rule-IPv4-
   Addr-Or-Prefix AVP, valid values of the IP-Prefix-Length AVP are from
   0 to 32 (full address) based on the different cases identified in
   Section 5.2 of [RFC7597].

3.9.2.  Rule-IPv6-Prefix AVP

   The Rule-IPv6-Prefix AVP (AVP Code 646) conveys the Rule IPv6 prefix
   and length as described in Section 2.4.  The Rule-IPv6-Prefix AVP is
   of type Grouped, as shown in Figure 10.

             Rule-IPv6-Prefix  ::= < AVP Header: 646 >
                                   { IP-Address }
                                   { IP-Prefix-Length }
                                  *[ AVP ]

                      Figure 10: Rule-IPv6-Prefix AVP

Top      ToC       Page 17 
   IP-Address (AVP code 518) is defined in [RFC5777] and is of type
   Address.  Within the Rule-IPv6-Prefix AVP, it provides the value of a
   unicast IPv6 prefix.  The AddressType field in IP-Address MUST have
   value 2 (IPv6).  Unused bits in IP-Address beyond the actual prefix
   MUST be set to zeroes by the sender and ignored by the receiver.

   The IP-Prefix-Length AVP (AVP code 632) provides the actual length of
   the prefix contained in the IP-Address AVP.  Within the Rule-
   IPv6-Prefix AVP, the minimum valid prefix length is 0.  The maximum
   value is bounded by the length of the end-user IPv6 prefix associated
   with the mapping rule, if present in the form of the Delegated-
   IPv6-Prefix AVP in the enclosing MAP-E-Attributes AVP.  Otherwise,
   the maximum value is 128.

3.9.3.  EA-Field-Length AVP

   The EA-Field-Length AVP (AVP Code 647) is of type Unsigned32.  Valid
   values range from 0 to 48.  See Section 5.2 of [RFC7597] for a
   description of the use of this parameter in deriving IPv4 address and
   port number configuration.

Top      ToC       Page 18 
4.  Attribute-Value Pair Flag Rules

                                                             +---------+
                                                             |AVP flag |
                                                             |rules    |
                                                             +----+----+
                                  AVP   Section              |    |MUST|
      Attribute Name              Code  Defined  Value Type  |MUST| NOT|
     +-------------------------------------------------------+----+----+
     |IP-Prefix-Length            632    3.1     Unsigned32  |    | V  |
     +-------------------------------------------------------+----+----+
     |Border-Router-Name          633    3.2     OctetString |    | V  |
     +-------------------------------------------------------+----+----+
     |64-Multicast-Attributes     634    3.3     Grouped     |    | V  |
     +-------------------------------------------------------+----+----+
     |ASM-mPrefix64               635    3.3.1   Grouped     |    | V  |
     +-------------------------------------------------------+----+----+
     |SSM-mPrefix64               636    3.3.2   Grouped     |    | V  |
     +-------------------------------------------------------+----+----+
     |Tunnel-Source-Pref-Or-Addr  637    3.4     Grouped     |    | V  |
     +-------------------------------------------------------+----+----+
     |Tunnel-Source-IPv6-Address  638    3.4.2   Address     |    | V  |
     +-------------------------------------------------------+----+----+
     |Port-Set-Identifier         639    3.5     OctetString |    | V  |
     +-------------------------------------------------------+----+----+
     |Lw4o6-Binding               640    3.6     Grouped     |    | V  |
     +-------------------------------------------------------+----+----+
     |Lw4o6-External-IPv4-Addr    641    3.6.1   Address     |    | V  |
     +-------------------------------------------------------+----+----+
     |MAP-E-Attributes            642    3.7     Grouped     |    | V  |
     +-------------------------------------------------------+----+----+
     |MAP-Mesh-Mode               643    3.8     Enumerated  |    | V  |
     +-------------------------------------------------------+----+----+
     |MAP-Mapping-Rule            644    3.9     Grouped     |    | V  |
     +-------------------------------------------------------+----+----+
     |Rule-IPv4-Addr-Or-Prefix    645    3.9.1   Grouped     |    | V  |
     +-------------------------------------------------------+----+----+
     |Rule-IPv6-Prefix            646    3.9.2   Grouped     |    | V  |
     +-------------------------------------------------------+----+----+
     |EA-Field-Length             647    3.9.3   Unsigned32  |    | V  |
     +-------------------------------------------------------+----+----+

   As described in the Diameter base protocol [RFC6733], the M-bit usage
   for a given AVP in a given command may be defined by the application.

Top      ToC       Page 19 
5.  IANA Considerations

   IANA has registered the following Diameter AVP codes in the "AVP
   Codes" registry:

           +------+----------------------------+---------------+
           | Code | Attribute Name             | Reference     |
           +------+----------------------------+---------------+
           | 632  | IP-Prefix-Length           | This document |
           | 633  | Border-Router-Name         | This document |
           | 634  | 64-Multicast-Attributes    | This document |
           | 635  | ASM-mPrefix64              | This document |
           | 636  | SSM-mPrefix64              | This document |
           | 637  | Tunnel-Source-Pref-Or-Addr | This document |
           | 638  | Tunnel-Source-IPv6-Address | This document |
           | 639  | Port-Set-Identifier        | This document |
           | 640  | Lw4o6-Binding              | This document |
           | 641  | Lw4o6-External-IPv4-Addr   | This document |
           | 642  | MAP-E-Attributes           | This document |
           | 643  | MAP-Mesh-Mode              | This document |
           | 644  | MAP-Mapping-Rule           | This document |
           | 645  | Rule-IPv4-Addr-Or-Prefix   | This document |
           | 646  | Rule-IPv6-Prefix           | This document |
           | 647  | EA-Field-Length            | This document |
           +------+----------------------------+---------------+

                        Table 1: Diameter AVP Codes

6.  Security Considerations

6.1.  Man-In-The-Middle (MITM) Attacks

   The AVPs defined in this document face two threats, both dependent on
   man-in-the-middle (MITM) attacks on the Diameter delivery path.

   The first threat is denial-of-service (DoS) through modification of
   the AVP contents leading to misconfiguration; e.g., a subscriber may
   fail to access its connectivity service if an invalid IP address was
   configured, the subscriber's traffic can be intercepted by a
   misbehaving node if a fake Border Node has been configured, etc.

   The second threat is that Diameter security is currently provided on
   a hop-by-hop basis (see Section 2.2 of [RFC6733]).  At the time of
   writing, the Diameter end-to-end security problem has not been
   solved, so MITM attacks by Diameter peers along the path are
   possible.  Diameter-related security considerations are discussed in
   Section 13 of [RFC6733].

Top      ToC       Page 20 
6.2.  Privacy

   Given that the AVPs defined in this document reveal privacy-related
   information (e.g., subscriber addresses) that can be used for
   tracking proposes, all these AVPs are considered to be security
   sensitive.  Therefore, the considerations discussed in Section 13.3
   of [RFC6733] MUST be followed for Diameter messages containing these
   AVPs.

7.  References

7.1.  Normative References

   [RFC1035]  Mockapetris, P., "Domain names - implementation and
              specification", STD 13, RFC 1035, DOI 10.17487/RFC1035,
              November 1987, <http://www.rfc-editor.org/info/rfc1035>.

   [RFC1123]  Braden, R., Ed., "Requirements for Internet Hosts -
              Application and Support", STD 3, RFC 1123,
              DOI 10.17487/RFC1123, October 1989,
              <http://www.rfc-editor.org/info/rfc1123>.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <http://www.rfc-editor.org/info/rfc2119>.

   [RFC2181]  Elz, R. and R. Bush, "Clarifications to the DNS
              Specification", RFC 2181, DOI 10.17487/RFC2181, July 1997,
              <http://www.rfc-editor.org/info/rfc2181>.

   [RFC4818]  Salowey, J. and R. Droms, "RADIUS Delegated-IPv6-Prefix
              Attribute", RFC 4818, DOI 10.17487/RFC4818, April 2007,
              <http://www.rfc-editor.org/info/rfc4818>.

   [RFC5777]  Korhonen, J., Tschofenig, H., Arumaithurai, M., Jones, M.,
              Ed., and A. Lior, "Traffic Classification and Quality of
              Service (QoS) Attributes for Diameter", RFC 5777,
              DOI 10.17487/RFC5777, February 2010,
              <http://www.rfc-editor.org/info/rfc5777>.

   [RFC5891]  Klensin, J., "Internationalized Domain Names in
              Applications (IDNA): Protocol", RFC 5891,
              DOI 10.17487/RFC5891, August 2010,
              <http://www.rfc-editor.org/info/rfc5891>.

Top      ToC       Page 21 
   [RFC6333]  Durand, A., Droms, R., Woodyatt, J., and Y. Lee, "Dual-
              Stack Lite Broadband Deployments Following IPv4
              Exhaustion", RFC 6333, DOI 10.17487/RFC6333, August 2011,
              <http://www.rfc-editor.org/info/rfc6333>.

   [RFC6733]  Fajardo, V., Ed., Arkko, J., Loughney, J., and G. Zorn,
              Ed., "Diameter Base Protocol", RFC 6733,
              DOI 10.17487/RFC6733, October 2012,
              <http://www.rfc-editor.org/info/rfc6733>.

   [RFC7596]  Cui, Y., Sun, Q., Boucadair, M., Tsou, T., Lee, Y., and I.
              Farrer, "Lightweight 4over6: An Extension to the Dual-
              Stack Lite Architecture", RFC 7596, DOI 10.17487/RFC7596,
              July 2015, <http://www.rfc-editor.org/info/rfc7596>.

   [RFC7597]  Troan, O., Ed., Dec, W., Li, X., Bao, C., Matsushima, S.,
              Murakami, T., and T. Taylor, Ed., "Mapping of Address and
              Port with Encapsulation (MAP-E)", RFC 7597,
              DOI 10.17487/RFC7597, July 2015,
              <http://www.rfc-editor.org/info/rfc7597>.

7.2.  Informative References

   [DSLITE-MULTICAST]
              Qin, J., Boucadair, M., Jacquenet, C., Lee, Y., and Q.
              Wang, "Delivery of IPv4 Multicast Services to IPv4 Clients
              over an IPv6 Multicast Network", Work in Progress,
              draft-ietf-softwire-dslite-multicast-10, August 2015.

   [PREFIX-OPTION]
              Boucadair, M., Qin, J., Tsou, T., and X. Deng, "DHCPv6
              Option for IPv4-Embedded Multicast and Unicast IPv6
              Prefixes", Work in Progress, draft-ietf-softwire-
              multicast-prefix-option-09, August 2015.

   [RFC3315]  Droms, R., Ed., Bound, J., Volz, B., Lemon, T., Perkins,
              C., and M. Carney, "Dynamic Host Configuration Protocol
              for IPv6 (DHCPv6)", RFC 3315, DOI 10.17487/RFC3315, July
              2003, <http://www.rfc-editor.org/info/rfc3315>.

   [RFC4607]  Holbrook, H. and B. Cain, "Source-Specific Multicast for
              IP", RFC 4607, DOI 10.17487/RFC4607, August 2006,
              <http://www.rfc-editor.org/info/rfc4607>.

   [RFC6052]  Bao, C., Huitema, C., Bagnulo, M., Boucadair, M., and X.
              Li, "IPv6 Addressing of IPv4/IPv6 Translators", RFC 6052,
              DOI 10.17487/RFC6052, October 2010,
              <http://www.rfc-editor.org/info/rfc6052>.

Top      ToC       Page 22 
   [RFC6334]  Hankins, D. and T. Mrugalski, "Dynamic Host Configuration
              Protocol for IPv6 (DHCPv6) Option for Dual-Stack Lite",
              RFC 6334, DOI 10.17487/RFC6334, August 2011,
              <http://www.rfc-editor.org/info/rfc6334>.

   [RFC6519]  Maglione, R. and A. Durand, "RADIUS Extensions for Dual-
              Stack Lite", RFC 6519, DOI 10.17487/RFC6519, February
              2012, <http://www.rfc-editor.org/info/rfc6519>.

   [RFC7598]  Mrugalski, T., Troan, O., Farrer, I., Perreault, S., Dec,
              W., Bao, C., Yeh, L., and X. Deng, "DHCPv6 Options for
              Configuration of Softwire Address and Port-Mapped
              Clients", RFC 7598, DOI 10.17487/RFC7598, July 2015,
              <http://www.rfc-editor.org/info/rfc7598>.

Acknowledgements

   Huawei Technologies funded Tom Taylor's work on earlier draft
   versions of this document.

   Special thanks to Lionel Morand for the detailed review.

   Many thanks to Russ Housley, Tim Chown, Spencer Dawkins, and Ben
   Campbell for the review and comments.

Top      ToC       Page 23 
Authors' Addresses

   Cathy Zhou
   Huawei Technologies
   Bantian, Longgang District
   Shenzhen  518129
   China

   Email: cathy.zhou@huawei.com


   Tom Taylor
   PT Taylor Consulting
   Ottawa
   Canada

   Email: tom.taylor.stds@gmail.com


   Qiong Sun
   China Telecom
   China

   Phone: 86 10 58552936
   Email: sunqiong@ctbri.com.cn


   Mohamed Boucadair
   France Telecom
   Rennes  35000
   France

   Email: mohamed.boucadair@orange.com